1. Field of the Invention
This invention relates to industrial screens of the type utilized in the dewatering and sizing of ore materials, coal, and the like.
2. Description of the Prior Art
The prior art industrial screens heretofore used in the foregoing fields are basically of two types. In one type an effort is made to produce a screen which is generally rigid. The desire to seek rigidity results from experiences with industrial screens which are vibrated during their operation. Thus screens which have wires which can slide one adjacent another during vibration of the screen are found to wear excessively. Screen rigidity prevents this type of wear but introduces the disadvantages that the rigidity of the screen wires prevents movement or vibrations effective to dislodge particles which, being close to the opening size of the screen, tend to blind the screen.
Examples of generally rigid screens of the foregoing type appear in U.S. Pats. No. 2,697,620, 3,327,853, and 3,716,144.
In the second type of screen, called a two-part interflexing screen, an effort is made to so construct the screen as to allow inter-vibration of the elements which form the screen, thus to prevent blinding. Two primary modes of vibration occur. One is a vibration of individual wire elements transverse to their length, and the other is a flexation or vibration of the support rods, which also vibrate transverse to their length. If such vibration is permitted to occur, screen blinding is no problem because the motions of the screen parts relative to each other readily knock out particles that would otherwise blind the screen because close to the opening size between adjacent screen wires. As obvious from the previous discussion regarding rigid screens, there remained a problem due to the poor life exhibited by the interflexing type of screen when vibrated, especially at high vibration frequencies.
Since the interflexing screens had only approximately half the life of rigid screens, interflexing screens were not frequently used for high speed vibratory screen applications until a stagger weld principle of the type disclosed in U.S. Pat. No. 2,690,265 was developed. The stagger weld principle was a compromise between the desires for a rigid long lasting screen on the one hand and for an interflexing non-blinding screen on the other hand.
In the stagger weld screen, groups of adjacent wires were welded together so as to vibrate as a unit without deleterious friction. This concept was an obvious compromise, however, because the welded groups of wires still blinded and still rubbed frictionally, one group with respect to the other.
As described in the following summary of the invention a substantial improvement in the operating life of industrial screens particularly of the interflexing type has been achieved through the use of a properly applied chrome plating.
U.S. Pat. No. 3,425,900 illustrates chromium plating applied to a woven screen. However, the use of a plating such as chromium to prolong the life of industrial screens appears not to have been employed in the art prior to the present invention.